This invention relates to photo processing machines, and in particular to apparatus for automating the recycling of developer and fixer chemicals in such machines.
In my co-pending application Ser. No. 07/617,522 filed Nov. 23, 1990 I described a system for recycling photographic developer. I have now discovered that similar principles can be utilized in connection with photographic fixers, as well. I have also discovered further ways to provide for recycling of both developers and fixers in small photo finishing equipment.
To date, it has been difficult and expensive to reuse and recycle fixers and developers. There are those who believe that it is merely necessary to cut back the replenisher rate for each film. For instance, if the normal rate is 100 cc, the recycling could be accomplished by reducing it to 50 cc. The problem with that approach, however, is that it does not account for the buildup of certain salts that can act to inhibit the photographic fixing process. The only way to avoid such a buildup is to redilute the used fixer with new fixer while continually removing a portion of the used chemicals.
The only method for doing so to date has been practiced only in large photo finishing plants and large hospitals, both of which have central mixing facilities. In those cases an operator could isolate several hundred gallons of used fixer and reintroduce that fixer into several hundred more gallons of new fixer. This process is expensive even for such large companies because of the labor-intensive nature of the work, and is simply unavailable for smaller companies.